Reenforced concrete structure



Jan. ll2, 1932. s. J. BRANsoN 1,840,304

REENFORCED CONCRETE STRUCTURE Filed Nay 31, 1928' Tin Patented Jan. 12,1932 UNITED STATES PATENT OFFICE SAMUEL JOSEPH BRANSON, OF EVANSTON,ILLIOIS, .ASSIGNOR, BY MESNE ASSIGN- MENTS, TO THE BR-ANSON SYSTEM,INC., F GHICAGO,`-'ILLINOIS, A. CORPORATION or DELAWARE ApplicationL ledMay 31,

My invention relates to reenforced concrete structures and it has forits object the provision of'anew and improved form and arrangement ofconcrete and reenforcing steel whereby both the concrete and thereenforcing steel shall have the maximum efficiency in operation forbuilding up tension, compression, and diagonal tension or shear, Wherebythe thickness of the combination floor and ceiling structure may be keptto a minimum consistent with proper strength, whereby the dead weight ofthe floor structures throughout the entire building may be greatlyreduced so as to correspondingly reduce the load to be supported by thegirders, columns and foundations of the building and vthus cut down thecost of the entire building structure, whereby the necessity for the useof lath and 'plaster shall be eliminated, and whereby in other respectsthe cost of production of the building maj7 be reduced.

It is one of the objects of my invention to provide a slab vloorstructure, supported by beams or other supports in spaced relation toeach other, and formed continuous over such spaced beams, comprising ineach slab section between the supports an improved arrangement ofconcrete and reenforcing steel whereby substantially the full depth ofthe slab maybe efective depth for developing Y tension and compression,while at the same time 'each of said sections between the supportingbeams is kept in the form of a slab strictly speaking, as distinguished-from a A beam' and slab type of construction, Whereby substantially thefull depth of the slab may be eiiective also for developing diagonaltension. It is one of the objects of my invention to provide aconstruction of this type in `which theV positive or bottom tensionmembers are located at the best possible position both with respect topositive or topk compression and alsowith respect to diagonal tension,whereby the greatestpossible depth of slab is effective depth for bothof such stresses. For attaining such novel construction by whichsubstantially the full depth of the slab is effective with respect toboth positive compression and diagonal tension, I have arranged bottomtension members substantially at the REENFORCED CONCRETE *STRUCTURE`1928. Serial No. 281,673.

plane of the bottom face of the slab, bonding the tension members to theslab by means of concrete pads or ribs formed integrally with the slabat its bottom face, such pads being of suflicient size to afford thedesired protection against fire and corrosion.

It is another object of my invention to provide an improved constructionof this type comprising a continuous slabsupported by beams or othersupports arranged in spaced relation to each other, with top tensionbars in transverse position with respect to the supports and imbedded inthe slab sulliciently below its upper face for proper protection againstlire and corrosion, in which construction the arrangement may be such asto provide the required compressivel strength for effective cooperationwith the top tensioning 4bars for attaining the desired margin ofsafety. To this end, it is one of the objects of my invention to providegreater compressive strength at the bottomvportion of the slabunderneath the top tensioning bars adjacent to said supports than isnormally provided hy the slab itself of even. thickness throughout, suchincreased bottom compressive strenvth adjacent to the supports beingprovided lay the use of bottom reenforcing bars in transverse positionwith respect to the supports and located substantially at the plane ofthe bottom face of the main portion of the slab, such bottom reentorcingrods being bonded to the slab by means of concrete pads or ribs formedintegrally with the slab at its bottom face, such pads being ofsuilicient size to aii'ord the desired protection against tire andcorrosion. It is one of the objects of my invention to provide such anarrangement that the saine steel bars act as the bottom compressionmembers for the edge portions of the slab adjacent to the supports andas the bottom tension members for the middle portion of. the spanbetween the supports, the portion of the bar which is not directlyactive with respect to any particular force which tends to deorm theslab serving as anchoring means for the remaining portions of the bar.ln the arrangement as specified, the bottom reenforcing bars develophigh vcompressive stresses in conjunction with the extreme fiberstresses of the concrete.Y

It is another object of my inventiori'to increase still further thebottom compressive stresses at the points adjacent to the supports, orthe negative compressive stresses as they are called, in cases in whichsuch further strengthening is required, such reenforcementv beingprovided preferably by osetting the bottom face of the slab downwardlyadjacent to the supports to a slight extent with respect to the bottomface of the main portion of the slab, such downward offsetting servingpreferably to bring Vthe bottoni faces of the edge strips of the slabsinto alignment with the bottom faces of the pads or ribs. j lt isanother-obj ect ofiny invention to pro- *vide an 'improved constructionof this type, iv'olvingfthe' use of bottom reenforcing steel runningboth *ways through they slab between the oppositelyldisposed supports,with such Y "bottom tensioning bars located substantially at the planeofthe bottom'face of the slab and "with such reenforcing bars bonded to"thes'labbyfpads or ribs of concrete formed integrally 'with the slab atits bottom face, in 'which the protecting and bonding ribs or pads areofsuch size and shape andare spaced yaft'such intervals with respectto`each other 'thata'n integrally formed mold may readily be v'used foreach of the `panels* between the 'ribssothatthe slab bottom portion andthe .adj acentiribside portions may benioldled and joinedsmoothlywithout any occasion yfor d isfliguri'ngimarks in theconcrete,thereby giving";the bottom fface of the slab ,as a whole ianattractiveappearance as a paneled molded i ling-and inale'unnecessary the use oflath d plasterer other additional lmoldings in y'conn'eotionwiththeconcrete. y

' Itis another object of'my invention to prove structures of kthis type`in vsundry detailsf'hereinafter pointed out.y The preferred means bywhich I'have laccomplished my sev- Y eral objects are'illustrated in theaccompanydrawings and are hereinafter specifically described. 1flhatwhich Ibelieve to be new and'fde's'iret'o cover by thisapplication issetforth the l'cl-aims.

fFig.- li-s avertical section'tliroughone form ofrmyimfproved floorstructure, being a Vfragmentary view-and showing also a portion ofoneiof the beams by which the floor structure is supported .at one side;

Fig. 2 is la vertical section taken substanv tially lat line 2-,2 ofFig. l;

Fig. 8 is a view similar to Fig. 2 but show .injg a modified form ofconstruction; and

"Fig, 4 vis :a cross section upon a reduced scale sho-wing theconstruction as shown at Ref'e'rringno'w particularlyto Figs. 'l and A2, l0 indicates the beams which stand in spa-ced'relartion toeach otherfor supporting sired spaced relation for supporting a continuous slabbuilt over and between the supports. In the construction illustrated inliigs. l and 2, the beams 10 are shown vas being` formed integrally withthe floor struc- -ture and strengthened by I-beams l1.

The door structure between the oppositely disposed longitudinallyextending supports l0 is in the form of a continuousslab 12of's'ubstantially uniform effective thickness throughout the entire spanbetween the supaorte. f

lt-eac'h'edge Vportieri of Vthe slab adjacent Vto the Isupporting beam,a series -of toptension members 'i3 are provided, such tension membersbeing in the forni of'steel'rods or bars extending transversely acrossIthe beams near .thetopv face of the slab, beingpo-sit'ioned as'near 'aspossible to the top face ofthe slab consistently with proper protectionof the bars bythe concrete against lire and ,corrosion( As is 'best'indicated yin 2, a plus rality ofthe tension bars lare connected togetherzbynieans of wires ll into the form of 'a' grill, legs 15 of anysuitable typebeingprovided on the grill .forsuppor'ting the bars 13 inthe desired position upon the form upon which Vthe'concrete-ispoured.For the intermediate portion ofthe sl'ab'between the supports 10,bottoni tensioning rods 16 are piovided, 'located substantially fattheplane of the fbottom face'of'tlie intermediate portion of the slab l2,-suc'li'bottoni'tensionrods 16 extendnigcontinuously rfrom one supportto the other at 1the level indicated Vand serving at theirLend portionsvas bottom compression members. zFor bonding the rods 16 to the slab,pads or ribs 17 of concrete are provided on the bottom 'face of theslab-,being 4formed integrallywith the slab, such pads being ofsufficient `thickness to 'provide vthe desired protection' ofthe rodsagainst fiire and' corrosion and f-orproviding a strong 'bond betweenthe rods and the slab.

Asis well understood in connection'with a structure of this typecomprising a slab extending o'ver andfbetween a series of spacedsupports, there is, under'nornial conditions involving substantiallyequal spacing of theV thepoints of inflection are located at a dis--tance fromV the supports "corresponding'to approximately one-fifth ofthe span. The top tension rods 13 are accordingly made of such length asto extend at `each side of a support well beyond the normal ointofiniiection, such rods extending preferably about onefourth of thedistance across the span. The

bondjbetween one end portion of a top tension Irod 13 and theconcreteslab serves as the anchory for the opposite end portion of therod.y The bottom tension members 16 also are sufficiently anchored tothe slab by their end portions which extend Well beyond the point ofinflection at each side of the span. i n

' By reason of the ypositioning of thebottom tension rods 16 directl rat the bottom face of the main portion' o the slab, preferably incenteredposition with respect to the plane of the bottom'face,the'entire thickness of the slab vis-eifective for developingcompressive stresses, rendering the structure of maximum eiiiciencywithrespect to bot-h the steel and thegco'ncretein this regard.

As is Well understood in the art, the externalforces which cause failureof a reenforced concrete floor structure by reason of inadequatediagonal tension in the structure are eifective principally at the levelof the bottom reenforc-ement for the structure at the point where thefailure occurs( It follows accordingly that when deep reenforced ribsare .provided on the bottom face of a slab across the span, such ribsare required by themselves to provide all the diagonal tension necessaryfor supporting the span, the slab itself assisting very little if any atall in developing effective diagonal tension. By my construction, inwhich there is no deep reenforced rib or other reenforced or reenforcingstructural part between the main supporting members lower than thebottom face of the slab itself, eifectivediagonal tension stresses aredeveloped directly in the slab itself and the full section of the slabis effective for this purpose.

In a reenforced concrete iioor or similar structure, the compressiveforces are greatest at' the compressive face and decrease to zero at theneutral axis at some point between the compressive face and the plane ofthe' centers of the tensioning bars. By the location of the bottomreenforcing bars 16 substantially at thel bottom face of the slab withthe depth of concrete in the pads extending below the bars merelysuihcient for providing. protection against fire and corrosion, thebot-y tom compressive stresses in the slab adjacent.

to the supporting vbeams are very materially increased, in view of themuch greater compressive strength of the steel as comparedy with that ofthe concrete, steel having a compressivel strength of from ten tofifteen times that of concrete in a similar position.

By the use of my construction, I have provided the maximum vstrength inproportion to theV amount and weight of concrete required. With anallowable steel stress of eighteeny thousand pounds per square inch andan allowable concrete stress of seven hundred pounds per square inch onextreme fiber, my improved slab of a thickness of two and one-halfinches will span a distance of ten and one-half feet with a superposedload of forty pounds per square foot in the one-way construction abovedescribed. By the development and refinement of the slab structure bywhich Iam able to span a distance of ten and a half feet without the useof strengthening ribs, I have very materially cut down the amount ofconcrete necessary as compared with those constructions in which suchstrengthening ribs are used and I have thus greatly reduced the load tobe carried by the girders, columns and foundations of the building. f

Myconstruction has substantially as great an advantage as compared withan ordinary slab construction, in which thebottom tensioning bars arelocated above the lower surfacefor purposes of fire-proofing andbonding. In such construction,it is necessary that the slab be made froman inch to two inches thicker in order to provide the required positivecompressive stresses above such tensioning bars, such increase inthickness serving to increase the amount and the weight of the concretefrom forty to sixty per cent. or more.

In some ways, the greatest advantage of all in the use of myconstruction resides in the fact that thereby the over-all thickness ofthe combination floor and ceiling is very materiallycut down, bothbecauseof having the slab structure itself of less depth or thicknessand alsozbecause'of 'the fact that no lath and plaster are necessary. Ifeight inches be saved at each floor, a builder would be able to providetwenty-one stories by the use of my construction as compared with twentystories by the former constructions, all without in any way weakeningthe construction.

Referring now to the construction shown in Figs. 3 and 4, beams 18 areprovided in spaced relation to each other, with beams 19 also inspacedrelation to cach other in crossed position with respect to the beams 18,only one of the beams 19 being shown in the drawings. A column 2O of anyapproved type is shown as supporting the structure at `the juncture ofthe beams 18 and 19. The formof the beams 18 and 19 differs from that ofthe beam 10, but at either point any approved form may be used. Theconstruction shown in Figs. 3 and 4 is substantially the same as thatabove described in connection with Figs. 1 and 2, except that theconstruction shown in said Figs. 3 and L1 is what is known as thetwo-way construction, involving the use of reenforcing members-extendingboth Ways` through. the floor, In Ythis construction-V as-Shown, the ,slabk 21 l,1s

providedwithedge strip portionsQZ off-increased thickness alongeachvotits.; four side edges, such edge strip portions being. ot suchincreased thickness and ofl such Width as to provide thej desired.bottom --co1npi`essive strength forthe portionsotlieslab adjacent tolthe* beaniisv The bottointension rodsare .preferably placedasnearvaspossible to the piane ofthe bottom face of thema-in portion ofthe, slab in the construction shown, the

vbottoni tension'vmembers 'running in one direction being located .theirVVcenters slightly-belowsuch plane and the bottom tension' rodsQlsrunuing invtheepposite di: rection being positioned withthei-rvcenters slightlyl above suchplanej; this being. necessary inorder vtro-allen?. such bars 23 and 2d to pass each other. In therconstruction shown, a .single lbottoni tensimiing rod is used inl'ieuiof the,l two vbottom. v.tensinning rods idas-shownin Fig. l. In.the forni shown in said Eigs.3..anzd 4, top tensioning rods areemployedin transverse positionavith respect to leachjofthe beams I8- andit',AtheV top tensioning bars.d in yone .direction being indicated by :thenumerals. Q5 andthe iop tensioning bars,v inthe cross direction being'indicated bythe numerals 2.6, a.iplurality toward thegpoints offinflection. By reason of making. the edge stripsr of the slab oiincreased thickness, With the bottoni faces of the edge stripspreferably in alignment' with the bottomy faces of the padsv or ribs117'the eiiectivewthickness. of .the slab underneath the top tensionbars-13 is-inade to correspond substantially to the thickness of the.slab?, above the bottom. tension .rods wat-the center olif the spanWhere the topfcompressive stresses are the'greatest. The edgestrips'712: of in-v creased thickness are made of such Width as toextendinvvardly towardthe points of 1n-l flection .to such` a distance-as-to. provide the n desired. compressive strength forsuch edge.

portions By reason of theY decrease in, the compressive stresses towardlthe. point of inflectio'n,V itis notl necessary thattlie increased.thickness be continued..thegfull distance to they points ofiniectioneven when such; strips u of'inc'reased thickness are used. M'In any casemain portion Vo the slab ,develops the re'- quifredcornpression Vincooperation with kthe bottom compression bars yfor providing therequired support..V it will beunderstood that in many casesitjsnotnecessary fto make the edgestrips of increased thicknessbut that in suchcases edge strips of a thickness corresponding to the; thickness ofthem/ain portion of the slahderelop fthe required. conipressivestresseseven at thev points adjacent to the aces ofthe supporting beams..Y By the use of the two-Way construction k1n- Volvingthe :pads Vorribs28 extending in crossed. relationship toeach other,and either Withor Without the edge strips, .22 of increased thieknesscorrespondingto,the combined thickness ot the pads andthe main port-ionofthe slab,y a very attractive paneled ceiling.. is provided. vByusngcare With respect to the contour of the forms against which the yedgesofthe pads and theedgesof thev strips 22 areinoidedy a decorative eiiectis .produced Without'rieti-acting in any Vivay .iroin the eiiectiveness,of the structurel mech anicaliyiA The. arrangement is such 'that uponthe removal of thev forms the structureis ready `for receiving itsiin'al coats, of paint orY other decorations Without the necessity foremploying iathsor plasterupon the bottoni` face of the slab, thisA beingmade possihl'e lley* reason ofthe `fact-thatv the individual slab facesections are. ofsuch size that they can bevcast readilyupon integrallyformed molds pressed ronirsheet metalinto'shape Without joints or ribsof anytyqiie7 the parts ofthevniold against Which-the edge vportions ofthe ribsfor pads/are castheing also formed integrally with the .mold forthe slab face sectio'n. n 'n f y By theuse oinly improved constructionas describedy in connection. WithFigs. 8 and 4, I amV abl'et'o span adistance of approximately sixteen and a half feet both stays between thesupporting beams7- with an'allowable steel stress of eighteen thousandpoundsper square inch and an allowable concrete stress of seven hundredlpounds perinch on eXtreme liber, Without the'duse of strengtheningribs.V Y I am able thus to make a Vradical saving in the amount oilconcrete required', with its cor responding saving. throughoutl thestructure.

While l prefer to employ the form of construction as illustrated inVthe*drawings. it

is tobej. understood that I *do not limit' the:l

invention to the forni shownexcept' so far as the'claiinsjin'ayfbe solimited by the prior art.

clain'ii--UM` 'f" j l". In'l ay reen'torcedand fire-,proofconcretestructure, the' combination of a'plu'ra'lity of' longitudinallyextending' supports in spaced relation to each otlien. a slab'of'concrete eX- tendinggfroniV one support to' the other, re-

enorcing rods extending, in spaced relation to eachother between saidksupports atsubstantially the plane of the bottom face' of the slab, andpads of concrete formed-integrally with saidslabon its bottom face andserving to imbed said reenforcing rods between the slab and the pads,said slabv otconcrete and' said imbedded rodsserving by themselves.

by theircooperation -to support theirown weight from said supports andalso to carry a predetermined additionalload.v e 1 2.In a reenforced andYlire-proof 'concrete structure,the combination ofa pluralityr ottlongit-udinally extending supportssin spaced relationto each other, aslab `ot concrete extending from one supportto the other,'reen`- fforcing` rods extending 1n, spjaced relation to each other between eachtwo successive supports at substantially the plane of the bottom face*lof the slab atfthe central portionthereot servingfas the bottom tensionmembers for the intermediate portion ofthe slab and extendingv onlyyslightlyeither above or below said plane atany point throughout theireffective tension portions whereby substantially rthe full section ofthe slab above such' rods is cffective Vfor developing; positivecompression,

and pads .of concreteformed integrally withV said slab onits bottomvface-and serving-to imbed saidreenforcing rods between the slabv andthe pads, saidslab of. concrete andsaid imbedded rods serving bythemselves Iby their'y cooperation to support their own-weight frommined additionalload. e. f n v 3.]In a reenforced. and lire-proofed'con-v crete structure, the combination. of a plurality Voflongitudinally extending, supports y inA spaced relation to eachother,:as1ab ofcon-v said supports and also` to crete' extending from.one. .support to` the other, reenforcing rods-extending in spacedVrelation to each other between saidsupports and each locatedatsubstantially the plane of the bottom face of the slab andalsoat thelowermost point of eilective Astresses in said struc- ;ture', and padsof concrete formed integrally with said slab on its bottom faceandserving to imbed 'said reenforcing rods between the slab and thepads. f. V. V.

4. In jay reenforced Vand .lire-proofconcrete structure, the combinationof a'plurality ofy longitudinally, extending supports yin Ispacedrelation to each other,I a slab of concrete ex'y tending from onesupport to theother, reen- `forcing rods for said slab extendingfinspaced relation to each other between each two successive supports,ywith the 'lowermost reen= forcing rods located substantially at.. theplane of the bottom face-of the slab at thel edge f portions ofthe slabYadjacenttothe supports `whereby the slab itself veloping diagonaltensiomandpads'of conis efective tor de-y creteformed integrally v,withsaid slab onits bottom face and serving to. imbedusaid re'v enforcingrodsbetween the slab,A and the pads, said slab, of'conorete and saidfimbeddedrods carry af-predeterspaced relation to eachother,-

bottom face ot the slab, and pads of concrete formed integrally withsaid slab on its bottom face and servingte imbed said reenforcing rodsbetween the slab and the pads throughout'the full span from one supportto the other, the central portions of the rods serving as the bottomtension members for the intermediate' portion of the slab and extendingonly slightly either above or below the plane ofthe bottom face of theslab at anypoint throughouttheir effective tensioning portions wherebysubstantially the full section of the slab above saidreenforcing rods iseffective for developing positive compression,y and the end portions ofthe rods serving as thev lowermost reenforcing elements of the structureadjacent to said su ports whereby the slab itself is effective orvrespect to the yslab as to cause substantially the full-.depth of theconcrete of the slab to' be 'effective for building up both positivecompression anddiagonal tension. 4 Y 7. ln a reenforced and tire-proofedconcretestructure, the combination of a 'plurality of longitudinallyextending supports in a slab of concrete extending from one support tothe other,

reenforcing'rods extending in spaced relationl to each other betweensaid supports in a single horizontal plane, and pads of concrete formed`integrally with said slab on its bottom face and serving to imbed saidreenforcing rods between the slab and the pads,tbe arrange- =.ment beingsucht that substantially the full depthy of the concrete of the slab iseffective for developing top compression at the middle portiono'f theslab and for developing diagonal tension in the portions ot proachingthe supports. f

8. In areenforced and tire-proofed conthe slab. ap-

crete structure, the combina-tion of a plurality of longitudinallyextending` supports in .spaced relation to each other, a slab'ofconai:mamma dbi mev ,am

way paneled bottom face on the slab ready for decoration, said slabcomprising at its edges adjacent to said supports edge strips ofsubstantially as great thickness as the combined thickness of the padsand the intermediate portion ot' the slab.

lil. ln a reen'liorced and tire-prooted concrete structure, thecombination of two longitudinally extending supports in spaced relationto each other, two other longitudinally extending supports in spacedrelation to each other and in cross relationship to said iirst namedsupports, a slab ot concrete extending between said several supports,recntorcing rods extending in spaced relation to each other between twoof said supports, other reenforcing rods extending in spaced relation toeach other between the other two supports, all ot said reenforcing' rodsbeing positioned substantially at the plane of the bottom face ot theslab, comparatively shallow and narrow pads ot' concrete formedintegrally with said slab on its bottom face serving to imbed saidreenforcing rods between the slab and the pads and serving to provide atwo-way paneled bottom face on the slab ready. tor decoration, and otherreenforcing rods imbedded in the slab and bonded therewith near the topface ot the slab at the edge portions adjacent to said supports servingas the top tension members for said edge portions of the slab, said slabcomprising edge strips of substantially the same thickness underneathsaid third named reentorcing rods adjacent to said supports as thecombined thickness ofthe pads and the intermediateportion of the slab,said edge strips being of such width transversely from the supports toprovide adequate compressive strength with respect to said top tensionrods.

l5. ln a reentorced and tireproofed concrete structureythe combinationot a longitudinally extending support, a slab of concrete supported atone edge by said support and evtendinn` laterally therefrom, areentorcing rod alongside ot' said support in spaced relation thereto atsubstantially the plane ot the bottom face of the slab` and a Dad otconcrete formed integrally with the slab on its bottom face about saidyrod and serving` to bond the rod directly to the slal wherebysubstantially the full depth ot the concrete ot tbe slab is eiective tordeveloping top compression with respect to the rod at its middle portionand tor developing diagonal tension at the end portions ot the rod.

lo. ln a reentorced and tireproo't'ed conrete structure.v thecombination ot a longitudinally extencinfr support, a slab of concreteeitending laterally from the support at both sides tbereot and supportedthereby at the parts adiacent thereto` reentorcino alongside ot saidsupport at opposite sides thereof respectively in spaced relationthereto at substantially the plane of the vbottom face of the slab, andpad-s of concrete formed integrally fwithvth'e'lslrab fon its bottomtace about saiclrodsserving to bo-nd the rods directly totlieslabwhereby substantially the tu-l-ldepthof the concrete of the slabis effective for developing top compression with res pec'tto-the rods attheir middle portions and for developing diagonal tension at the endportions ofthe r'odsjv p '17. In a reenforced and lireproofed concretestructure, the combination of a plurality of 'longitudinally eirtendingsupports in spaced relation toeach other-,transverse supporting means4connecting said first named supports inseries, `a slab of concreteextending over thefiiitermediate spaced supports and connecting 'theoutermost spaced supports alongside of said transverse supporting means,reenforcing rods extending between adjacent spaced supports in spacedrelation to the transverse supporting means at substantially the planeot the bottom face of the slab, and pads of concrete formed integrallywith the slab on its bottom face about said rods serving to bond therods directly to the slab whereby substantially the full depth of theconcrete of the slab is effective for developing top compression withrespect to the rods at their middle portions and for developing diagonaltension at the end portions of the rods.

18. In a reenforced and ireproofed concrete structure, the combinationof two longitudinally extending supports in spaced relation to eachother, two other longitudinally extending supports in spaced relation toeach other in crossed relationship to said rst named supports, a slab ofconcrete extending between said several supports, reenforcing rodssecurely connected between each two spaced supports at opposite marginalportions of the slab in spaced relation to the cross-positionedsupports, each of said four reenforcing rods being positionedsubstantially at the plane of the bottom face of the slab. and pads otconcrete formed integrally with the slab on its bottom face serving toimbed the several reentorcing rods between the slab and the pads.

19. A reeniorced concrete structure comprising in combination a slab ofconcrete, a second slab of concrete of smaller depth formed integrallytherewith, a reenforcing bar extending across said thinner slab portionat substantially the bottom face thereof and extending into said thickerslab portion, and a pad of concrete formed integrally with said thinnerslab portion surrounding said reentorcing bar serving to bond said bardirectly with said thinner slab portion and merging at its end with saidthicker slab portion.

20. A reenforced concrete structure comprising in combination a slab ofconcrete, a

Zei,

Loud

second slab of concrete of smaller depth formed integrally therewith,I aseries of reenforcing bars extendingacross said thinner slab portion atsubstantially the bottom face thereof and extending into said thickerslab portion at spaced intervals therealong, pads of concrete 'formedintegrally with saidV thinner slab portion and surrounding saidreenforcing bers for bonding vthem directly to said thinner slabportion, said pads merging at their ends with said thicker slab portion,and a series of negative reenforcing bars extending across said thickerslab portion Y and into said thinner slabportion adjacent to the upperface of said united slab strucn ture,v said second named bars being insubstentially parallel Yposition With respect to said first namedreenforcing bars.V`

SAMUEL JOSEPH BRANSON.

